This project is concerned with the relationship between the structure and activity of proteins, particularly those of the immunoglobulin system. Studies are being carried out to determine the amino acid sequences and three-dimensional structures of Bence Jones proteins, immunoglobulins, 02-microglobulins from different species, and a variety of lectins. The purpose of these studies is to determine the relationship between the amino acid sequences and the folding of proteins as well as to correlate the structures of these proteins with their biological activities. New methods for fractionating lymphoid cells according to the specificity of their Ig receptors are being worked out and microanalytical techniques are being used to analyze the distribution, number and fate of lymphocyte surface receptors. Various populations of fractionated cells are being tested for their ability to reconstitute an immune response and methods are being devised to define cytoplasmic structures that modulate the distribution and mobility of surface receptors. The main goal of these studies is to define the conditions and events leading to the mitogenic stimulation of lymphocytes by lectins and by specific antigens.